Q.9.  In a dihybrid cross, if you get 9 : 3 : 3 : 1 ratio it denotes that

a.  the alleles of two genes are interacting with each other

b.  it is a multigenic inheritance c.   It is a case of multiple allelism

d.  the alleles of two genes are segregating independently

(d)  Alleles of two genes are segregating independently. It can be explained as. Suppose crosses are made between a pea plant with round and yellow seeds and ono with wrinkled and green ones.

All ${\mathrm{F}}_{1}$ hybrids give yellow and round seeds. Since yellow colour is dominant over the green and the round shape is dominant over hte wrinkled.

When the  ${\mathrm{F}}_{1}$ hybrids plants are crossed to each other or allowed to self fertilise, an  ${F}_{2}$-generation form as represented in the following figure

The outcome of the dihybrid cross make it very clear that segregation of the seed colour is independent of the seed shape and both the parental and new combinations of the characters appear in the ${F}_{2}$ offspring, i.e., an assortment of genes of one pair is independent of the other pair.

When the alleles of two interacting with each other one may dominate over other or become recessive. During a multigenic inheritance, we describe characteristics that is specified by a combination of multiple genes. Multiple alleles is a type of non-mendelian inheritance pattern that involves more than just the typical two alleles.